Back and Forward Buttons using simple code

This page was one of the first attempts I made to make it easy to update navigation on
the site. I wanted each page to reference the previous and next pages in the series. This
was OK, but after a while I kept adding pages and changing the order. This meant that lots
of pages had to be updated when I wanted to make a change. So my goal was to discover how
JavaScript could make updating less tiresome. This page is one of a series attempting to
solve this problem: Others in this series are:

This page was only a sampling of what could be done and is where I started. The user
could navigate through the tutorial, but I had to change the functions on every page,
which soon became tedious.

Click on the buttons below to get to the previous and to the next page in this
tutorial:

The arrows at the top of this page use exactly the same code. The code is activated by
the onClick event in the button or in the image code. The onClick calls,
respectively, the Back() and the Forward()
function. Here's the simple code in the head of this document:

Both the buttons and the images use this code to move to the next and previous pages of
the tutorial. The next attempt was to enable me to write code so I didn't have to update
every page when I made changes to one page.